1. Field of the Invention
The present invention relates generally to a frictional engaging apparatus for a fluidically actuated clutch or brake and more particularly to a fluid pressure supplying method and apparatus for a fluidically actuated frictional engaging apparatus for speed changing or direct shifting in a vehicle transmission.
2. Description of the Prior Art
Conventionally, a modulator valve is disposed within a conduit which supplies an actuating fluid pressure to a fluidically actuated frictional engaging apparatus for a vehicle transmission. The modulator valve is operable upon direct shifting or change-speed shifting and slowly increases the supplying fluid pressure, thereby reducing the engaging shock of fluidically actuated frictional engaging apparatus.
However, when the capacity of the fluidically actuated frictional engaging apparatus is large and the free stroke of a piston within the fluidically actuated frictional engaging apparatus, prior to initial engagement, is also large, it takes a relatively long time to engage the piston, and when the above-mentioned modulator valve is utilized, it takes even more time to engage the fluidically actuated frictional engaging apparatus and an unpleasant feeling is transmitted to the driver and idle racing of the engine with a loud roar occurs.
In this invention, line pressure or high pressure close to line pressure is supplied during the free stroke of a piston within a fluidically actuated frictional engaging apparatus and the piston in rapidly moved until initial engagement of the piston occurs whereupon the engaging pressure is lowered and is thereafter slowly increased, thereby smoothly engaging the fluidically actuated frictional engaging apparatus without shock while reducing the engaging time of the fluidically actuated frictional engaging apparatus.